A tilt box such as described in U.S. Pat. No. 4,342,412 is provided with rollers that rotate about respective axes normally perpendicular to the displacement direction of a continuously moving web passing over them. These rollers are carried on a frame pivotal about an axis perpendicular to the workpiece travel direction. When the web moves to one side or the other, that is crosswise of the displacement direction, the roller frame is pivoted appropriately to bring it back onto center. As the web is fed into the system it is often necessary to apply quite a bit of correction, before the production line is completely up.
Downstream of the tilt box at least one position sensor detects the transverse position of the web and feeds an appropriate output to a controller which is connected to a drive that can pivot the roller frame. The controller therefore adjusts, in a standard feedback-type system, the frame position by means of the drive in accordance with the detected web position. When the web is initially fed through the tilt box, same is normally centered, as the downstream sensor is only effective once the workpiece is loaded all through the line.
Typically the frame itself is provided with various position detectors. One establishes the above-mentioned center position and serves mainly when a new web workpiece is being threaded through the tilt-box rollers. Two others are positioned when the frame is in extreme end positions, and serve normally to shut down the system since in these extreme end positions further overtravel and tearing of the web is likely. Two further position detectors respond as the frame approaches the respective extreme end positions and normally are hooked up to sound an alarm so the machine operator can check what is happening and correct it, if possible without having to shut down the line.
This complex of position detectors is normally constituted as individual switches and actuators that are positioned all over the pivotal roller frame and its support. They are difficult to install and adjust, and are a clutter of wire that makes working on the machine fairly troublesome.